Purification of hydrogen peroxide by a nonconcentrating distillation



March 23, 1948. C, N, RlCHARDsQN 2,438,252

PURIFICATION OF HYDROGEN PEROXID BY A NON-CONCENTRATING DISTILLATION Filed Feb. 26, 1942 (5f/denier hunted y PURIFI-CA'IION 0F HYDROGEN PEROXIDE I BY A NONCONCENTRATING DISTIl'aLA'liIOvi` Chester Northup Richardson, Youngstown, N. Y., p zssignor to The Mathieson Alkali Works, Inc.,

New York, N. Y., a. corporation of Virginiay Application February 2s, i942, serial No. 432,419 l l This invention relates to improvements in the purification of aqueous hydrogen peroxide, and particularly to the separation therefrom of relatively non-volatile impurities. The invention is especially useful in centration,

inorganic impurities silica and the like.

unstable or they may odor or taste It is the object of the ford a simple and effective method mentioned and others, peroxide, and to produce inal impure'solution isfactory for commercial purposes.

Another object of sion of a method oi preparing tion, free -rom practical manner.

will be apparent as it is 2 volatile impurities including some less volatile than hydrogen peroxide, are removed by Vaporizinga large volume of water containing a small proportion of hydrogen peroxide from the solution to be purified and passing these vapors in the vapors, separating the thus without subwhich the hydrogen under subatmospheric The The water component of the conthe production of the pure 5 aqueous hydrogen peroxide of commercial concontact with the solution to vaporize the impurities, condensing Under certain methods of preparing hyrogen vaporized and condensed impurities from the peroxide, the product may be contaminated with water component, and returning the water comvarious impurities, some of which are relatively lo ponent to the solution. Volatile impurities are volatile and others relatively non-volatile. The vaporized by the partial pressure effect of the more volatile impurities are readily removable by vaporized water and, being present in but small known methods, and the present inventionis diproportion, can be eliminated rected4 to the separation of the relatively non-volstantial loss of hydrogen peroxide because of the atile impuritiesin solution or in suspension or relatively low proportion in partly in solution oi' present as colloids, including peroxide is vaporized with respect to water and such as iron, nickel, copper, because the bulk of the vaporized hydrogen mercury and other metals and their compounds, peroxide is returned to the solution with the These impurities, even in vaporlzed and subsequently condensed water traces, may render the aqueous hydrogen peroxide after separation of the impurities. This vaporiimpart undesirable color, zation is best carried out to the product. pressure; an absolute pressure not exceeding present invention to afabout 100 mm. of mercury is advantageous.

of separating impurities, being principally immiscible with relatively non-volatile impurities, includingthose water, can vbe separated largely from the confrom aqueous hydrogen densed vapors by permitting stratification to take thereby a commercial place and then separating the stratied aqueous product having substantially the same concenand oily material. This separation can be facilitration of hydrogen peroxide as that of the origtated by extracting the condensed vapors with a but free from such impurisolvent immiscible with water such as toluene or ties and consequently stable and otherwise satone `of the other solvents used in the production of hydrogen peroxide by oxidation of organic lnthe invention is the prov'- termediates.

aqueous hydrogen` densed vapors, after separation of impurities, is peroxide of constant and commercial concentrawith .advantage returned to the aqueous hydroimpurities, in an economical and gen peroxide solution undergoing purification in v the region Within which vaporization of water Other objects and advantages of the invention and volatile impurities is effected.

better understood by Such preliminary treatment, if necessary, releference t0 the OUOWD@ Speciiication andthe 40 moves the more volatile impurities from the accompanying drawing, in which Fig. 1 is a graph illustrating .the equilibrium between the liquid and vapor phases of hydrogen peroxide at varying concentrations and temperatures and at absolute pressure oi.' 23 mm. of mercury; and

Fig. 2 is a diagrammatic illustration of an apparatus suitable for the practice of the invention. it being understood that details familiar to the art and unnecessary for the purpose of explaining 'the invention are omitted in the interest of clarity. l

The aqueous hydrogen peroxide as initially recovered may include both volatile and non-volatile impurities. If volatile impurities are present, they should be removed first by any suitable procedure. A satisfactory procedure for this purpose is disclosed in U. S. Patent No. 2,298,064, granted October 6, i942, for Chemical manufacture. In accordance with this procedure,

aqueous hydrogen peroxide and affords a solution adapted to be further purified in accordance with the present invention. The solution still includes the lessv volatile impurities which are not readily removablein a simple and convenient manner by methods available prior to the present invention. Indeed. there were available no satisfactory data on the basis of which the present invention could have been predicated, be-

cause the equilibrium between liquid and vapor.

phases in hydrogen peroxide solutions had not been determined accurately and with sufficient completeness to permit the development of a methoddepending upon distillation and condensation of the distillate without risking the possibility of concentrations in the solution which are known to be unstable, that is above 50% to 60%. The presence of such concentrations introduced the dificulty oi possibly serious explosions. It was necessary, therefore, first to carry -may be Withdrawn through a l point to condense most of out extensive experimental work directed to the determination of the-constants for the liquid and `vapor phasesv at varying concentrations and temperatures. For this purpose, a suitable subatmospheric pressure was selected, namely 23 mm. of mercury, as best adapted to maintenance of the operation in commercial practice by the use of a suitable vacuum pump. As the result of this investigation, the equilibrium data were determined and plotted as shown in Fig. 1 of the drawings, in which the concentrations of the vapor (condensate) and of the corresponding liquid at any given temperature can be readily-determined. With such information and the knowledge that a concentration of 45% hydrogen peroxide is stable and therefore safe, it became possible to develop a simple distillation method whereby a hydrogen peroxide solution of given concentration can be recovered while the relatively non-volatile impurities are retained at the point of distillation and can be purged from time to time as-they accumulate. 'I'he condensate of pure hydrogen peroxide is a commercial concentration which may be varied within the limits fixed by the phase equilibrium conditions and, by maintaining the'conditions in a predetermined manner, the concentration of the product can be made uniform.

In carrying out the invention, any suitable apparatus may be utilized, as .for example the arrangement diagramamtically illustrated in Fig. 2 of the drawing, in which 5 indicates a still which is supplied with heat from a source 6 and is fed with the impure hydrogen peroxide through a pipe 1 at a uniform rate. The vapor from the still passes through a leg 8 to a condenser 9 which may be supplied with cooling water or other suitable fluid in a jacket ill through an inlet pipe II and outlet pipe l2. .The circulation of the cooling water is regulated to maintain the desired temperature of condensation. n

'I'he condensate, consisting of the pure hydrogen peroxide solution in the desired concentration, is delivered to a receiver I3 from which it pipe I4 controlled by a valve i5. 'I'he product thus obtained is pure hydrogen peroxide solution free from the nonvolatile impurities and of the required concentration. It need not be subjected, therefore, to any further treatment other than by one of the stabilizing methods well known in the art.

The uncondensed vapor passes through a leg i6 to a second condenser i1 having also a jacket i8 which is supplied with Water or other cooling 20. of the condenser is maintained at the desired the remaining vapor which is largely water containing a relatively small amount of hydrogen peroxide. This condensate is Withdrawn through a pipe 2| and returned to the still 5. Thus, any substantial loss of hydrogen peroxide is avoided.

The remaining uncondensed vapor and gases, consisting of decomposition products and a relatively small quantity of hydrogen peroxide, are withdrawn through the pipe 22 and the vacuum pump 23 and discharged. The impurities which accumulate in the still may be withdrawn from time to time through a purge 24.

As hereinbefore indicated, it is possible in the operation of the simple apparatus described to` regulate the conditions so as to recover pure hydrogen peroxide free from non-volatile impurities and of desired commercial concentration. Thus,

for example, if 100 parts by weight per* hour of 27.4% hydrogen peroxide are introduced through the pipe 1 to the still 5, it may be observed by reference to Fig. 1 that at absolute pressure oi' 23 mm. of mercury maintained by the vacuum pump 23, the concentration 'of the solution in the still can be maintained at 45% hydrogen peroxide. provided a temperature of 38 C. is maintained in the still. This will result in the vaporization of 349 parts per hour of 10% hydrogen peroxide. If then the condenser 9 is operated by adjusting the ow'and temperature ofthe cooling water so that the vapor temperature is about 31.5 C., 98.5 parts by weight of 27.4% hydrogen peroxide will condense and will be delivered to the receiver i3. This constitutes the product of the operation and is a satisfactory concentration for commercial use.

The remainder .of the vapors, amounting to 249 parts by weight per hour, containing 3% of hydrogen peroxide, passes tothe condenser i1 which is maintained at a temperature of approximately 5 C. This weak solution of hydrogen peroxide returns through the pipe 2| to the still 5 where it is added to the feed and revaporized in the still.

The un-condensed residue of vapors and gas,

27.4% hydrogen peroxide, passes through the pipe 22 and vacuum pump 23 and is discharged. This small loss actually includes also the small amounts of non-volatile impurities which accumulate in the still and are purged from time to time. Consequently the overall eiiciency of the operation is extremely high, the losses other than those due to impurities being negligible.

The apparatus employed, or that part of it in contact with aqueous hydrogen peroxide, is constructed of glass of composition inert with respect to hydrogen peroxide. Appropriate materials of construction .include Pyrex glass. Silica, stoneware, "tin, some stainless steels, some alloys of aluminum and enameled iron and steel may also be used. Materials tending catalytically to decompose hydrogen peroxide, such as ordinary steel and nickel, for example, should of course be avoided. While reference has been made to hydrogen peroxide produced by oxidation of organic intermediates in solvents immiscible with water, the

invention is of general application in the purification of hydrogen peroxide solutions where the purified solution is to be recovered at a definite concentration. The invention is therefore, to the purication of concentrated aqueous solutions of hydrogen peroxide, however produced, which may have been contaminated in any manner with any relatively nonvolatile impurities.

The advantages of the invention include purification of high degree in respect to less volatile and non-volatile impurities, including both organic and inorganicimpurities, low losses of hydrogen peroxide due to incidental decomposition, the avoidance of hazards of destructive decomposition, simplicity of control and economical operation.

. the invention 1. 'I'he method of separating an aqueous hydrogen peroxide solution from relativelynonapplicable, f

volatile impurities which comprises heating the solution under vacuum at a substantially constant temperature such that a safe concentration is maintained, condensing a portion of the vapor under vacuum at a substantially constant temperature adapted to afford a condensate having a concentration of hydrogen peroxide substantially the same as that of the original impure aqueous hydrogen peroxide solution subjecting the remaining vapor to a second -condensation at a lower temperature and returning the second condensate to the solution.

2. The method of separating an aqueous hydrogen peroxide solution from relatively nonvolatile impurities which comprises heating the solution under vacuum at a substantially constant temperature such that a safe concentration is maintained, condensing a portion of the vapor under vacuum at a substantially constant temperature adapted to aord a condensate having a concentration of hydrogen peroxide substantially the same as that of the original impure aqueous hydrogen peroxide solution subjecting the remaining vapor to a second condensation at a lower temperature, returning the second condensate to the solution and withdrawing the uncondensed residue.

3. The method of separating an aqueous hydrogen peroxide solution from relatively nonvolatile impurities which comprises continuously feeding an impure aqueous hydrogen peroxide solution, heating the solution under vacuum at a substantially constant temperature such that a safe concentration is maintained, condensing a portion of the vapor under vacuum at a substantially constant temperature adapted to aord a condensate having a concentration of hydrogen peroxide substantially the same as that of the original impure feed, subjecting the remaining vapor to a second condensation at a-lower temperature and returning. the second condensate to the solution.

4. The method of separating an aqueous hydrogen peroxide solution from relatively nonvolatile impurities which comprises continuously I feeding an impure aqueous hydrogen peroxide solution, heating the solution under vacuum at a substantially constant temperature such that a safe concentration is maintained, condensing a portion of the vapor under vacuum at a substantially constant temperature adapted to afford a condensate having a concentration of hydrogen peroxide substantially the same as thatfof the original impure feed, subjecting the remaining vapor to a second condensation at a lower temperature, returning the second condensate to the solution and withdrawing the uncondensed residue. l

5. The method of separating an aqueous hydrogen peroxide solution from relatively nonvolatile impurities which comprises heatingl the solution under vacuum to a temperature equivalent to that which at a pressure or 23 mm. of mercury will maintain a concentration not higher than 45% hydrogen peroxide, condensing a portion of stantially constant temperature adapted to anord a condensate having a concentration o! hydrogen peroxide substantially the same as that of the original impure aqueous hydrogen peroxide solution subjecting the remaining vapor to a. second condensation at a lower temperature and re turning the second condensate to the solution.

the vapor under vacuum at a sub- 6. The method of separating an aqueous hydrogen peroxide solution from relatively nonvolatile impurities which comprises heating the solution under vacuum to a temperature equivalent to that which at a pressure of 23 mm. of mercury will maintain a concentration not higher than 45% hydrogen peroxide, condensing a portion of the vapor under vacuum at a substantially constant temperature adapted to afford a condensate having a concentration of hydrogen peroxide substantially the same'as that of the original impure aqueous hydrogen peroxide solution subjecting the remaining vapor to a second condensation at a lower temperature, returning the second vcondensate to the solution, and withdrawing the uncondensed residue.

'7. The method of separating an aqueous hydrogen peroxide solution from relatively nonvolatile impurities which comprises continuously feeding an impure aqueous hydrogen peroxide solution, heating the solution under vacuum to a temperature equivalent to that which at a pressure of 23 mm. of mercury will'maintain a concentration not higher than 45% hydrogen peroxide, condensing a portion of the vapor under vacuum at a substantially constant temperature adapted to afford a condensate having a concentration oI hydrogen peroxide substantially the same as that of the original impure feed, subjecting the remaining vapor to a second condensation at a lower temperature and returning the second condensate to the solution.

8. The method of separating an aqueous hydrogen peroxide solution from relatively nonvolatile impurities which comprises continuously feeding an impure aqueous hydrogen peroxide solution, heating the solution under vacuum to a temperature equivalent to that which at a pressure of 23 mm. of mercury will maintain a concentrationnot higher than 45% hydrogen peroxide, condensing a portion of the vapor under vacuum at a substantially constant temperature adapted to afford a condensate having a concentration of hydrogen peroxide substantially the same as that of original impure reed, subjecting the remaining vapor to a second condensation at a, lower temperature, returning the second condensate to the solution, and withdrawing the uncondensed residue.

CHESTER NOR-THU? RICHARDSON.

REFERENCES CITED The following references are of record in the rile of this patent:

UNITED STATES PATENIB Number Name Date 898,980 Lowenstein Sept. l5, 1908 1,145,162 Moest July 6, 1915 1,536,213 Halvorsen May 5, 1925 1,924,954 Muller Aug. 29, 1933 1,937,682 Boedecker et al. Dec. 5, 1933 2,081,097 Reinders May 18, 1937 2,091,218Y Schmidt Aug. 24, 1937 2,210,438 Adolph Aug. 6, 1940 2,282,184 Harrower May 5, 1942 FOREIGN PATENTS Number 'Country Date 330,255 Great Britain May 20. 1930 445,334 Greet Britain Apt. 7, 1936 

